Thermotic pump



S. HENDERSON THERMOTIC PUMP April 18, 1944.

Filed June 25, 1941 INVENTOR ATTORNEYS W Patented Apr. 18, 1944 .UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to a thermotic pump and more particularly to such a pump which is actuated by the expansion and contraction of air by the application and withdrawal of heat. Such a pump has been found to be particularly useful as a breast pump and for eflecting drainage in many fields of surgery, particularly in urology.

One of the principal objects of the invention is to provide such a pump which is particularly adapted for use as a breast pump or for effecting drainage in surgery, the pump being readily designed to have a low value suction and on and oil periods of short duration, thereby to efiect a gentle drainage and to release the flesh drawn again the catheter following each suction period so as to render the catheter operative for drainage during the next suction period.

Another object is to provide such a pump which can be used either as a suction pump or as a pressure pump,

Another object is to provide such a pump which has accurately controlled on and of! periods of uniform lengths.

Another object is to provide such a pump in which these on and oil periods can be made of short duration thereby to provide a thermotic pump having high air handling capacity.

Another object is to provide such a pump which is practically noiseless in operation.

Another purpose is to provide such a pump in which an electrical heating element is employed as the heat source and in which the element is so designed as to rapidly heat the air and also rapidly cool when deenergized.

Another object is to provide such a pump which can be readily designed or adjusted to have any desired capacity'or to develop any desired degree of pressure or suction.

Another aim is to provide such a pump having no major moving parts and which will stand up under conditions of severe and constant use without getting out of order or requiring repairs.

In the accompanying drawing:

Fig. 1 is a diagrammatic representation of a thermotic pump embodying my invention and the circuit therefor, the pump being shown as used in conjunction with a-conventional suction bottle for efiecting drainage in surgery.

Fig. 2 is a side elevation of a breast pump embodying my invention.

Fig. 3 is a diagrammatic representation of the circuit employed in the operation of the breast pump shown in Fig. 2.

The form of the invention shown in Fig. l is adapted for use for surgical drainage, and is shown as connected by a suction tube 5 with the short stem 6 of a conventional suction bottle 1, the long stem 8 of which is connected by a tube 9 with the catheter (not shown). The liquid drawn through the suction line 9 from the wound or cavity being drained is trapped in the suction bottle 1.

The thermotic pump is diagrammatically shown in Fig. 1 as including a cylinder l5 having and heads l6 and I! forming a' cylindrical working chamber l8. This cylinder and its end heads are preferably made of aluminum so' as to be light in weight and so as to readily dissipate the heat generated in its working chamber.

The cylinder I5 is shown 'as connected with a valve housing 20 by a tube 2 I, this valve housing being conventionally illustrated as having a cen tral chamber 22 in communication with the working chamber l8 of the cylinder l5 through the an upper exhaust chamber 23 having an exhaust port 24 leading to the atmosphere; and a lower suction chamber 25 having a nipple connection 26 with the suction tube 5 leading to the suction bottle 1. An upwardly opening exhaust check valve 21 is conventionally shown as controlling the escape of air from the chamber 22 into the exhaust chamber 23 and an upwardly opening suction check valve 28 is conventionally shown as controlling the flow of air from the suction chamber 25 into the chamber 22.

With apparatus as above described it will be seen that upon heating the air in the working chamber 18, this air will be expanded and forced out through the tube 2|, check valve 21, exhaust chamber 23 and through the exhaust port 24 to the atmosphere. Upon then. allowing the air in the working chamber l8-to.

cool, its contraction on cooling will draw air .from the suction bottle 1 through suction tube 5, nipple 26, and suction chamber 25 past the suction check valve 28 and through the chamber 22 andtube 2! into the working chamber I8 of the cylinder I5. .Alternate suction and pressure producing periods are thereby provided, the pump being capable of being employed either as a suction or as a pres sure pump.

The dissipation of the heat from the air in the Working chamber l 8 is efiected by conduction through the walls of the cylinder and the heating of the air in theworking chamber is eiiected by an electrical heating element indicated generally at 39. The heating element is shown as including two end disks 3| made of mica or other suitable dielectric material and each supported inthe working chamber I8 adjacent one of the end heads l6, 1.! in coaxial relation to the cylinder chamber 22, exhaust.

IS in any suitable manner. The edges of these mica disks 3! carry the loops of a resistance heating wire or filament 32, the loops of this resistance heating wire or filament being strung be tween the edges of the mica disks in closely spaced relation and so as to extend around the full periphery of each of these disks. One terminal of this resistance heating wire or filament 32 is shown as extending through an insulator 33 in the end head I! to oneside 34 of a mainv power line which supplies power at, say, 110 volts, and the other terminal of the resistance heating wire or filament 32 is shown as extending through a similar insulator 35 to the slide wire resistance of a rheostat 35. It is an important feature of the present invention that the resistance heating wire or filament 32 be as fine as possible and that it be spread along the entire inner wall of the working chamber. To this end the resistance heating wire or filament is preferably in the order 01*.002 in'chin diameter and strung upon the mica disks;3.ll in the; manner described. By using such fine; and widely'distributed'jwire or filament Has the heatingelementthe wire or filament heats and cools rapidlythereby to provide shorter cycles and pump more air. in a given period of time; a greater current can be passed through the filament without danger of burningit out'because of the short period: ofrenergization required; because of this increased capacity higher positive ornegative pressures can: be developed by thepump; and thermalilag is reduced: because of the high rateof heat transfer between'the resistance heatingjwire or filament 32 and thesurrounding air inthe working, chamber I8.

The-other side 40 of. the main power line is shownas connected. througha line switch 4 i' and plug. socket 42 to' a line 43 connecting a pilot light 44; across the mainpowerlineand toa line 45 connecte'diwitha microswitch or snap action switch 45.. The. plug socket-His for the receptionv of: the; plug of 1 an; extension switch (not shown) SDi'iihSjt the pump can be turnedgon and ofiirom. aremote point... When either this extension. switch or the line switchuil isclosed, the

pilot light 44': is, of course; illuminated to indicate that fact. Themicroswitch is carried by a fixed. bracket or frame 50 to which is also fixed one end ofra'bimetallic arm l on the free end of which is arranged. an adjusting screw 52 in. position. to engage the operating button of the microswitch 46. This bimetallic. arm is surrounded 'bya resistance wire 5.3, one terminal of which is connected directly with the side 34 of the main power line and theother terminal of which can he -connected through an adjustable resistor 54 with a line: 55Z1eading to the rheostat: 36 and to the other terminal of the microswitch 45.

In the operation of. the form of' the-invention illustrated in Fig. 1, when the line switch 4!, or the extension switch (notshown) connected with the plug. socket 42; is closed, current flows from the side 40 of the main. power. line through the line 43 and pilot light 44 to the other side 34 of the main power line, and also flows through the line45, closedmicroswitch'46, line 55, rheostat 38, resistance heating wire or filament 32 to the other side 34 of themain power line. At the same time,'current from the closed microswitch SB-passes from line 55 through the adjustable resistor.54, and through resistance wire 53 5L1- rounding the bimetallic :arm- 51 tothe other side 34' of the main. power line.

The energization of the resistance heating wire or filament'3-2 causes this fine, widely spread wire to rapidly heat the air confined in the cylindrical heating chamber l8, this expanding the air and causing it to discharge through the tube 21, chamber 22 of the valve housing 20 and past the exhaust check valve 21, exhaust chamber 23 and exhaust port 24 to the atmosphere. During this energization of the resistance heating wire or filament 32, the resistance wire 53 surrounding the bimetallic arm 5| is also heated thereby causing the bimetallic arm to; flex and engage its screw 52 with the button of the microswitch 4i; and open this switch. The opening of the microswitch 46 breaks the circuit through the resistance heating wire or filament 32 and hence this resistance heating Wire or filament and the surrounding air begins to cool, the heat being conducted through the walls of the cylinder !5. This cooling of. the air in the working chamber 13 causes it to contract, thereby to draw air from the suction bottle I through suction tube 5, nipple 25 and suction; chamber? 25 and; past, suction check valve- 28,, chamber 1 22-- and tube, 2i into the 'working chamber I13;

ing chamber 18- with the developmentof a greater negative or positive; pressure .inthe-xinletiand outlet ports, respectively;,otthevalve housing Zii.

When it is desired to: vary'the volumeof air handled by the pump, this is readily doneby adjusting either the adjusting: screw 52 of; the bimetallic arm 5+ orthe adjustableuresistancei Backing away the adjusting screw 'fiflyrequireszthe bimetallic arm to be; heated to a" higher-tempera ture before; it opens the microswitch; 4'.Ei='and hence slows the-timing of' this thermostatically controlledswitch; Slowingofgthis timing of this thermostatically controlled microswitch 46;. of course, slows thetimingmf. then-pump andresults in a smaller'volume of'air handled by the pump. Slow or fast timing of theoperationof the thermostatically controlledmicroswitch 46 can. also obviously be obtained byadjustment of. the ad justable resistor 54. It. will therefore. be. seen that either the adjusting SCIGW'Z52 or: the adjustable resistor 54 can'be employedifor this purpose, both being-shownby'way of illustration.

It is desirable that the temperature of the pump cylinder Il'rbe maintained'asllow as possible and that the pump becapable of adjustment to reduce the on and off periods to asshort a time as possible. Thus, by-reducing the time necessary to reach maximum air pressure in'the working chamber [.8 andby-reducing the time necessary to cool' this air, arr-increased. amount ofair is handled-and the size of; pump to handle a given amount ofaircan be reduced; This rapid timing of the pump is in large measure achieved by the fineness and spacing of the resistance heatin wires or filaments 32. With such fiiner wires there is a rapidtransfer of heat from the wires to the air and cooling of these wires following energization, thus reducing the thermal lag of the pump; and the wires heat up more rapidly both because of. the greater resistance prov'idedby the and is not responsive to the air temperatures de, veloped in this working chamberbut to the temperature of a resistance in parallel with the heating element in the working chamber. If the thermostat or bimetallic arm were responsive to the air temperature in the working chamber l8 there would be a decided lag in the operation of the pump both because of the lag in the heating of the air and its transfer to the thermostat and because a much more rapid heating of this thermostat can be achieved by the use of a metallic arm were responsive to the temperature of the air in the Working chamber l8, its timing would change with the changes in temperature of the cylinder forming this chamber. By having the bimetallic arm entirely independent of the temperatures developed in the working chamber, it can be timed as fast as may be desired and this timing will be continued as long as the pump is in operation.

A valveless breast pump embodying the invention is illustrated in Figs. 2 and 3. The breast pump is shown as including a tubular metal holder 60 having a bottom or base 6| and open at its top to receive the bottle 62 into which the milk is drawn. The upper end of the holder 60 is preferably cut away, as indicated at 63, both to show the amount of milk in the bottle 62 and also to permit of the holder being sprung to firmly grip the bottle and provide a unitary structure. The bottle 62 is shown as provided with a removable cap 64 having an arm 65 leading to a suction cup 66 which is held against the breast when the pump is in use. The arm 55 is provided with a passage 61 leading from the suction cup 66 through a tube 68 into the bottle 62. Intermittent suction and pressure is created in the bottle 62 through a stem 69 in its cap, this stem connecting with a tube 10 leading to the pressure unit which is entirely housed Within the bottom of the tube 60.

This pressure unit and its circuit is identical with the pump shown in Fig. 1 except for the omission of various controls, these being unnecessary in view of the specific use for which the breast pump is designed. Specifically, the pressure unit shown in Fig. 3 is valveless and it does not have the line switch, plug socket, pilot light, rheostat and adjustable resistor as with the form of the invention shown in Fig. 1. Since in other respects the two forms of the invention are identical, the same reference numerals have been employed.

The tube 2| leading to the working chamber of the cylinder I5 is connected directly to the tub 10 leading to the interior of the bottle 62, the valve housing being eliminated. One ter minal of the resistance heating wire or filament in the cylinder I5 is connected directly with the one side 34 of the main power line and the other side 40 of this main power line is connected directly with one terminal of the normally closed microswitch or snap action switch 46. This resistance wire as shown at 53. Further if the 121- switch is mounted on the bracket or frame 75 which also rigidly supports one end of the bi metallic arm 5|. This bimetallic arm carries the adjusting screw 52 which is arranged to engage and actuate the button of the microswitch 46. The bimetallic arm 5| is surrounded by the'resistance wire 53 one terminal of which is connected with the line 55 which connects With the other terminal of the microswitch 46 and also with the other terminal of the resistance heating wire or filament within the cylinder IS. The other terminal of th resistance wire 53 is connected directly with the other side 34 of the main power line.

The breast pump shown in Figs. 2 and 3 is adapted to be held in the hand and its main power line is merely plugged in to establish the circuit through the pressure unit, no line switch being necessary. After being so plugged in, the cup 66 is held against the breast. The current from the side 46 of the main power line passes through the closed microswitch 46, line 55, and through the resistance heating wire or filament in the cylinder l5 to the other side 34 of the main power line. The heating of the air contained in the cylinder I5 causes it to expand and be expelled through the tubes 2| and 10, and stem 69 into the bottle 62. The pressure so built up in the bottle 62 escapes through the stem 68, arm 65 and cup 66 past the breast against which the cup 66 is held, the breast yielding to permit the escape of the warm air.

While the resistance heating wire or filament in the cylinder I5 is so being energized, current is also passing from the line 55 through the resistance wire 53 around the bimetallic arm 5! to the other side 34 of the main power line. The heating of this resistance wir 53 causes the bimetallic arm 5! to flex until its adjusting screw 52 engages the button of the microswitch 46 to open this switch. The timing of the thermostat control for the microswitch 46 is effected by adjustment of the screw 52. This opening of the microswitch 46 opens the circuit through the resistance heating wire or filament in the cylinder l5, thereby permitting the air in its working chamber to cool.

The cooling of the air in the Working chamber of the cylinder causes it to contract thereby creating suction in the bottle 62 through its tube connections 2!, l0 and 69. The suction in the bottle 62 causes the breast to be drawn firmly against the cup 66, the milk being Withdrawn and flowing down the stem 68 into the bottle 62 where it is collected.

When the resistance wire 53 and the bimetallic arm 5! cools, the bimetallic arm is permitted to flex so as to release the button of the microswitch 46 thereby permitting this microswitch to close. This cycle of operations is repeated as long as the breast pump is plugged in.

From the foregoing it will be seen that the present invention provides a thermotic pump which is particularly adapted for use in the sur gical field and as a breast pump, although the invention is not, of course, limited to any particular field of use but is to be accorded the full range of equivalents comprehended by the accompanying claim. It will be seen that a pump embodying the invention is noiseless; free from moving parts; is reliable in operation; is not likely to get out of order; can be designed to have a high capacity and develop high pres sures, either positive or negative, and is fully adjustable in both regards.

I claim (as my invention:

A thermotic pump for therapeutic use in effecting the intermittent drainage of fluids, comprising a housing forming a working chamber provided with end heads and with 'a' metal side wall through which heat is readily conducted from the 'gasyv'ithin said chamber and dissipated to the exterior, a duct leading irom said working chamber exteriorly of said. casing, a :single source of electrical current, an electrical heating element-in said chamber and comprising dielectric end supports arranged adjacent said end heads and a fine resistance heating filament looped back and forth between said end supports in closely spaced relation to each other and in closely spaced parallel relation to said side wall, the fineness of said filament permitting to rapidly heat and, when deenergized, to rapidly dissipate its heat 'to the gas in said -"cbam'b'er, and the close proximity of said filament to the metal side wall of said chamber permitting the heat of said filament, when deenergized, to be rapidly conducted through the thin layer of gas outside of said filament to said side Wall of said chamber and dissipated thereby, a switch arranged remote from and substantially unafiected by changes in temperature of said housing and connected to place said filament in circuit with said single source of electrical current, means arranged remote from and substantially unafiectedby Changes in temperature of said housing and actuated by said single source of electrical current to alternately open and close said switch, and means associated with said duct to provide a substantially unidirectional flow of gas through said chamber in response to the intermittent heating of the gas in said chamber by said filament.

STANFORD HENDERSON. 

